Polybutylene terephthalate resins are used as engineering plastics in wide fields including automobile parts, electric and electronic parts, or the like owing to their excellent mechanical properties, electric properties, and other physical and chemical properties, and their good workability. In particular, since their heat resistance and strength can be increased by adding a fibrous filler such as glass fiber thereto, polybutylene terephthalate resins are often used by reinforcing thereof by the fibrous filler.
Particularly in the field of automobiles, polybutylene terephthalate is often used as a material of sensors used for electrical control and housings of ECU. Since such a product requires low warpage, it is often alloyed with a noncrystalline resin, such as polycarbonate, or added with an inorganic filler of a high aspect ratio in flakes or powder.
On the other hand, for the parts (insert molded articles) being mounted in an environment of severe temperature increase/decrease, such as engine room of automobile, the toughness of the parts is often improved by adopting an elastomer and the like to prevent crack generation caused by strain resulting from the difference in linear expansion between metal and resin. However, a large amount of an elastomer is required to be blended to achieve sufficient resistance to heat shock and there has been a problem of reduction in the strength. In particular, as described above, the resistance to heat shock is prone to be reduced in a system where alloyed with a noncrystalline resin, such as polycarbonate, or added with an inorganic filler of a high aspect ratio in flakes or powder to achieve the low warpage, and it has been difficult to have both the resistance to heat shock and the low warpage.
Although JP-A 53-121843 discloses that low warpage are improved by combining a fibrous filler with a plate filler, this material is low in resistance to heat shock.
In addition, although JP-A 4-169214 describes that the adhesion with an inserted metal is improved by blending polycarbonate and a fibrous and/or nonfibrous filler in polybutylene terephthalate, there is no description regarding the resistance to heat shock, and in reality, in such a composition, the resistance to heat shock is insufficient.
Further, although JP-A 8-311312 describes that the morphological stability and the flexural toughness at low temperatures are improved by blending polycarbonate and a core shell polymer in polybutylene terephthalate, there is no description regarding the resistance to heat shock, and in reality, in such a composition, the resistance to heat shock is insufficient.